qat.experimental.dialect.gate.transforms.naive_placement module

A pass that assigns each algorithmic qubit to a physical one by rewriting its type.

The pass uses a naive placement approach to assign qubits.

class AllocDetail(alloc_op, is_algorithmic, place, drop, qubit_values, dealloc_op)

Bases: object

What the pass learned about one qubit allocation before any rewriting.

Variables:

  • alloc_op – The AllocateQubitOp being analysed.

  • is_algorithmic – Whether the allocation is for an algorithmic qubit

  • place – Whether the qubit is to be kept and placed on a physical qubit.

  • drop – Whether the qubit is to be dropped (unused)

  • qubit_values – Every SSA value in the qubit’s chain, after the allocation result to the last gate result, in order.

  • dealloc_op – The DeallocateQubitOp ending the chain, or None.

alloc_op: AllocateQubitOp
dealloc_op: DeallocateQubitOp | None
drop: bool
is_algorithmic: bool
place: bool
qubit_values: list[SSAValue]
class NaiveQubitPlacementPass(qubit_view, policy, explicit_qubit_ids=None)

Bases: OrderedPass, ModulePass

A pass that assigns each algorithmic qubit to a physical one by rewriting its type.

The pass uses a naive placement policy to assign qubits, which can be one of:

  • best_coupling: assign qubits to the highest fidelity or best coupled physical qubits (1 or 2 qubits only). Inputs that mix physical and algorithmic qubits are rejected.

  • explicit: assign qubits to the physical qubits specified in the explicit_qubit_ids

  • as_written: assign qubits to the physical qubits in the order they are allocated

Unused allocated qubits are dropped (including those that are deallocated before any use). The pass will raise an error if a two-qubit gate is applied to uncoupled qubits. Couplings are directed, so the qubit view must list a link in both directions for a gate to be accepted either way round.

Functions that take or return qubits are rejected and should be inlined first. The input module must be valid, as for any xDSL pass.

The pass validates up front so the module is left unchanged if validation fails.

apply(ctx, op)

Replace each algorithmic qubit allocation with a physical one under the chosen policy and remove any unused allocations. Inputs with physical allocations are processed without change apart from validating the qubit indices.

Parameters:

  • ctx (Context) – xDSL context (unused).

  • op (ModuleOp) – Module to optimize.

Return type:

None

explicit_qubit_ids: tuple[str, ...] | None = None
name: ClassVar[str] = 'gate.naive-qubit-placement'
policy: PlacementPolicy
qubit_view: QubitView
class PlacementPolicy(*values)

Bases: StrEnum

The policy used to assign algorithmic qubits to physical ones.

as_written = 'as_written'
best_coupling = 'best_coupling'
explicit = 'explicit'